1. Field of the Invention
This invention generally relates to color barcodes type of machine-readable symbology for encoding digital data, and more particularly, it relates to a method for increasing the data capacity of color barcodes for high capacity data encoding and decoding.
2. Description of the Related Art
Color barcodes are a type of machine-readable symbology for recording digital data. Conventional one-dimensional and two-dimensional black and white barcodes are widely used. Recently color barcodes have also been introduced to increase the data capacity of the barcodes, one more “dimension” being added to the barcodes in addition to the intensity of light reflection to represent additional data, and are often referred to as “three dimensional (3D)” barcodes. For example, U.S. Pat. Nos. 7,478,746, 7,533,817, 7,751,585 and 8,006,911 proposed various ways of encoding data with color barcodes. Due to relatively poor color reproducing fidelity during the printing and imaging process, the number of colors that can be used in a given barcode is limited. Thus additional measures should be taken to further increase the data capacity of color barcodes. U.S. Pat. No. 7,751,585 utilized color triangles instead of conventional rectangles/squares to reduce barcode size and thus increase its data capacity; U.S. Pat. No. 8,047,447 suggested to use printer halftone dot orientations of each of the primary printing color channels to increase the amount of encoded data.
Color printers are typically used to produce color barcodes on recoding media such as paper, transparency, plastic sheet, fabric, etc. Color printers generally use toning materials, such as color inks and toner particles, of the subtractive colors, i.e., cyan (C), magenta (M) and yellow (Y). These colors (C, M and Y), together with black (K), are usually referred to as the CMYK colors or the CMYK color space. To a certain extent, colors printed by a printer depend on the characteristics of the toning material sets used by the printer.
Oftentimes color barcodes may be displayed on a color display device such as a cathode ray tube (CRT) monitor, a liquid crystal display (LCD) monitor, etc. Color displays generally use display pixels having additive colors, i.e., red (R), green (G) and blue (B). These colors (R, G and B) are usually referred to as the RGB colors or the RGB color space.
In addition, a color scanner, camera or other detecting device is often used to scan or read a color barcode. A color scanner or detector typically uses a set of color filters (e.g. RGB filters) to detect the color of the received light.
With the increased use of barcodes and the advancement in technology that enhanced the resolution of color printers, displays and scanners, it is desirable to introduce new ways for increasing the data capacity of color barcodes for high capacity data encoding and decoding.